1. Field of the Invention
The present invention relates to a device that intermittently transmits a driving force suitable for driving, the paper supply roller of, for example a facsimile machine, an optical character reader (OCR), or a printer.
2. Description of Prior Art
Any conventional paper supply device incorporated in data transmission equipment such as a facsimile needs to intermittently feed paper. Conventionally, rollers for supplying papers are intermittently driven by using electromagnetic clutch means. FIG. 1 represents the conventional structure of a paper supply device for a facsimile. First, an explanation of such a conventional paper supply device is given. Any conventional paper supply device is provided with a stacker 1 which loads paper 2, and a paper supply path between a lower guide plate 3 and an upper guide plate 4 for conveying the paper 2 to the left-end of the mechanism shown in FIG. 1. A paper forwarding roller 6 is provided at the end of stacker 1 to make a pair in combination with a pressure roller 5 which is pushed down by a spring (not shown in FIG. 1), thus making it possible to carry forward one or several sheets of paper 2 by the rotation of the paper forwarding roller 6 in the arrowed direction. A separation plate 9 is provided in a position right above a paper supply roller 7 and which is pressed against the surface of the paper supply roller 7 by a spring 8. When the paper supply roller 7 rotates in the arrowed direction, only the sheet on the bottom is separated from the rest of papers 2 and carried to the left. A reader 11 is provided in a position forward of the paper supply roller 7, where the first paper feed roller 12 and second paper feed roller 13 are provided to respectively make up pairs in combination with pinch rollers 14 and 15. The delivered paper 2 then passes through the paper supply path between a lower guide plate 16 and an upper guide plate 17 before eventually being delivered to a discharger 18 shown at the left of FIG. 1. A light source 19 illuminates the paper supply path, while light reflected from the paper supply path is directed to the optical character reader (not shown). The length of each roller correctly matches the width of the papers 2, or a plurality of rollers are aligned to the correct width. FIG. 2 shows an example of a conventional driving mechanism of the paper supply device shown in FIG. 1. The driver unit is provided respectively with a paper forwarding gear 6a coaxially installed together with the paper forwarding roller 6, a paper supply gear 7a coaxially coupled to the paper supply roller 7, a driver gear 12a coaxially coupled to the paper feed roller 12 and a pulley 12b, a driver pulley 21 driven by a motor (not shown), and a belt 22. The driver gear 12a is driven by the driver pulley 21 via the belt 22, while the rotation force of the driver gear 12a is transmitted to the paper forwarding gear 6a via an idler gear 23, the paper supply gear 7a, and a further idler gear 24, respectively. The rotation force of the paper forwarding gear 6a is transmitted to the paper forwarding roller 6 only when an electromagnetic clutch 26 is activated. The paper forwarding roller 6 is intermittently driven in response to the ON/OFF operation of the electromagnetic clutch 26, so that papers can be supplied intermittently. The other pulley 13b, driven by the belt 22, is also coaxially coupled to the second paper supply roller 13, while the paper supply rollers 12 and 13 are constantly rotated by the pulleys 12b and 13b. As a result, papers 2 which were intermittently supplied by these means are then continuously carried by the paper supply rollers 12 and 13. In particular, when operating a facsimile machine, papers 2 are intermittently supplied to the reader 11 from stack 1, but continuously sent forward when passing through the reader 11, as a result, the paper supply device needs to execute both intermittent and continuous paper supply operations. There are two methods of executing these operations, either by employing a single driver system as described above, or by providing a driver system for each function. When executing these two functions by applying a dual driver system, although the driving force can be transmitted by using a relatively simplified mechanical structure, it results in greater overall size of the structure, making it difficult to meet the need for compactness. In light of such requirements, the conventional driver mechanism uses a single driver system as shown in FIG. 2. However, when a single driver system is applied, the mechanical structure unavoidably becomes complex, moreover, a clutch mechanism is needed for executing intermittent driving. To compensate for this, an electromagnetic clutch is often used. However, when an electromagnetic clutch is introduced, the major cost of the intermittent driver mechanism is the electromagnetic clutch, and since a compact electromagnetic clutch is quite expensive, it adversely affects the total cost. In addition, since the transmission force and performance of the driver mechanism significantly depend on the precision of the component parts of electromagnetic clutches, a realization of the higher reliability of the intermittent driving mechanism will eventually result in higher cost. Furthermore, conventional techniques still need to apply special processes to the shafts before installing the electromagnetic clutches, thus involving higher production costs.